Biological materials as PIN FRs for PLA

Phosphorus-rich microalgae, biochar, phosphorylated lignin, zinc phytate and reduced sewage sludge ash were tested as flame retardants at 5 – 20% loading in poly lactic acid (PLA). The Desmodesmus sp. algae were subjected to darkness/phosphorus deprivation then light, resulting in biological “luxury” phosphorus uptake (reaching c. 0.9% P content). The cacao shell biochar and the treated sewage sludge ash both contained c. 5% P. The zinc phytate and phosphorylated lignin were both based on biomaterials (phytase, lignin) and contained respectively 13% and 3% P. The algae and P-lignin showed greater reductions in peak heat release rate (around one third reduction) despite not having the highest phosphorus content. The authors conclude that 10% loading of algae resulted in significant fire performance improvement without deteriorating polymer properties, opening the path for further research.

“Wastewater phosphorus enriched algae as a sustainable flame retardant in polylactide”, M. Dudziak et al., Polymer Degradation and Stability 227 (2024) 110885 https://doi.org/10.1016/j.polymdegradstab.2024.110885